Recently, control of an electronic device mounted in an automobile is performed by using a hardware unit including a microcomputer called an electronic control unit (ECU) as disclosed in U.S. Pat. No. 6,898,500B2 (JP 2004-122803A). Also in many cases a single ECU performs control of a plurality of electronic devices. In this case, input/output of a signal to the ECU is made via a terminal pin (for example, a terminal pin disposed for mounting the ECU as a hardware unit to a socket in a side of the automobile), and an input terminal pin and an output terminal pin are individually allocated to each electronic device.
However, even in the same type of automobiles, the control content (i.e., function) of each electronic device having the similar hardware is required to change depending on a difference in specification between the automobiles. In this case, according to the conventional method, the contents of the control software are provided to be different from one another corresponding to the required function, and the control software in accordance with each specification is stored.
However, where a plurality of electronic devices is provided in a single automobile, the devices may have the same hardware and differ in function from one another, and only allocation of the function to each electronic device may differ depending on the specification of the automobile. For example, when the same kind of the electronic devices are mounted at two locations of a first position and a second position in the automobile and one of the electronic devices is controlled to perform an A-function and the other thereof is controlled to perform a B-function, a first specification in which the A-function is allocated to the electronic device at the first location and the B-function is allocated to the electronic device at the second location is defined independently from a second specification in which allocation of the functions is opposite to that of the first specification. That is, the B-function is allocated to the electronic device at the first location and the A-function is allocated to the electronic device at the second location.
In this case, the line-up of the plurality of functions used in the same automobile is the same regardless of the difference in the specification and only the allocation of the functions differs depending on the position of the electronic device. Accordingly, a demand for sharing the software between the first specification and the second specification naturally occurs in a designer's mind. This, however, raises the following problems.
That is, in a case of sharing the software of the A-function and the software of the B-function between the above two specifications, when a relation between the software of the functions and terminal pins is fixedly determined so that terminal pins designated for the software of the A-function are P1 and P4 and terminal pins designated for the software of the B-function are P2 and P3, it is obvious that in the first specification, the electronic device at the first location is required to be connected to the terminal pins P1 and P4 and the electronic device at the second location is required to be connected to the terminal pins P2 and P3. On the other hand, in the second specification, the connection between the electronic devices and the terminals in the first specification as set above is required to be replaced. However, the situation where in an assembly line of the same kind of automobiles, terminal pins of the ECU connected to the electronic device located at the same position inside the automobile frequently change depending on the automobile specification is not practical also from a viewpoint of the problem with possible erroneous assembly. Therefore, the sharing of the software between the specifications has not been adopted yet.
Accordingly, when a plurality of electronic devices, each having the same hardware are disposed at different locations, it is more advantageous, from a viewpoint of a stance of an assembly manufacturing site, to fixedly determine which terminal pins of the ECU the electronic device should be connected to in accordance with an assembly position of the electronic device to the automobile. In this case, it is required to provide the software in which the designation of the terminal pins as the input/output points of the automobile is variably changed with each specification, thus raising the problem of inefficiency.